Data transmission method and data transmission device

ABSTRACT

A data transmission method capable of suppressing communication errors with a simple microcomputer processing is provided. Upon a pulse signal in which specific data is made up of H and L levels, either one of which has a pulse width taken as a first fundamental signal length T 1  and the other of which has a pulse width taken as a second fundamental signal length T 2  equal to an integer multiple of the first fundamental signal length T 1 , a correction is performed by increasing or decreasing the second fundamental signal length T 2  by a length equal to an integer multiple of a value resulting from dividing the first fundamental signal length T 1  of the transmission-side pulse signal by an integer.

TECHNICAL FIELD

[0001] The present invention relates to a data transmission method and adata transmission device for constructing specific data by means of thepulse widths of H and L levels.

BACKGROUND ART

[0002] Recently, with the spread of electric home appliances equippedwith an infrared radiation type wireless remote control (hereinafter,referred to as infrared remote control), there has arisen a problem thatproducts may misidentify other manufacturers' signals or signals derivedfrom other products, resulting in malfunctions. Due to this, theAssociation for Electric Home Appliances (AEHA) intends to prevent theoccurrence of such malfunctions by prescribing a data transmittingsignal format for the infrared remote control. The following describesthe construction of this signal format defined by the Association forElectric Home Appliances.

[0003]FIG. 2 shows the construction of the signal format. As shown inthis figure, a signal sequence consists mainly of a leader L indicatingthe start of the signal sequence, a custom code C(C₀, C₁) identifyingthe company that supplies the product, a parity P, a data codeD(D₁-D_(n)) indicating specific information to be conveyed and a trailerTR indicating the end of the signal sequence. These are transmitted inthis order to execute one control command. Of these signals, FIGS. 3A-3Cshow the shapes of standardized major pulse signals. That is, FIG. 3Ashows the shape of the pulse signal in the leader portion L, FIG. 3Bshows the shape of the pulse signal in the data code portion D and FIG.3C shows the shape of the pulse signal in the trailer portion TR. Thesesignals are constituted by pulses whose widths are integer multiples ofa fundamental signal length T. As shown in the figures, a substantiallyrectangular pulse signal composed of H and L levels is designed to makeup specific data depending on the H level pulse width and the L levelpulse width so that what signal has been transmitted and received can bediscriminated by detecting these pulse widths. Specifically, if a signalis transmitted whose ratio of the H level pulse width to the L levelpulse width is 8T: 4T as shown in FIG. 3A, this signal is decided as aleader L indicating the start of the signal sequence. If a signal istransmitted whose H level pulse width is T and whose L level pulse widthis 8 ms or longer as shown in FIG. 3C, this signal is decided as atrailer TR indicating the end of the signal sequence.

[0004] Meanwhile, the shapes of pulses in the data code portion Dindicating the information are dependent on how “0” and “1” data arecombined as shown in FIG. 3B. Each of the data is distinguished from theother by H level pulse width and L level pulse width. That is, if theratio of the H level pulse width to the L level pulse width is T:T(1:1), the received data is recognized as “0” data. If the ratio of theH level pulse width to the L level pulse width is T:3T (1:3), thereceived data is recognized as “1” data. It is also prescribed that theratio of the sum of the respective level pulse widths of “0” data tothat of “1” data should be 1:2. Further, the fundamental signal length Tis prescribed to fall within in the range of T=350 μs-500 μs, 3T=1050μs-1500 μs).

[0005] In this connection, there has been a problem that if the pulsesignal of the data code portion D is transmitted as it is in the exactwaveform prescribed by the signal format, communication errors tend tooccur because the waveform on the reception side is unsharpened on thewhole as shown in FIG. 5 depending on the infrared photodetector'scharacteristics, noise-reducing capacitor and so on, resulting in shiftsin the ON/OFF timing of the waveform. More specifically, the waveformrecognized by a microcomputer on the reception side is affected bythreshold settings, with a tendency that H level pulse widths on thetransmission side are recognized longer and L level pulse widthsshorter. Therefore, the waveform on the reception side may not satisfythe prescribed requirements of the range of fundamental signal length,T=350 μs-500 μs, and the ratio among the individual pulse widths, as aproblem.

[0006] It is conceivable to adopt a method in which, as shown in FIGS.6A-6D, L level pulse widths of a transmission-side waveform are setlonger than its H level pulse widths, more specifically, a method inwhich the L level pulse width is corrected to an integer multiple of theH level pulse width before transmitted. That is, in this method, on thetransmission side, the ratio of H level pulse width to L level pulsewidth for “0” data in the transmission waveform is set to T:2T as shownin FIG. 6A, and the ratio of H level pulse width to L level pulse widthfor “1” data is set to T:5T as shown in FIG. 6B. As a result of this, onthe reception side, the ratio of H level pulse width to L level pulsewidth for “0” data and “1” data in the reception waveform becomegenerally 1:1 and 1:3, respectively, as shown in FIGS. 6C and 6D. Inthis case, however, there arises a problem that pulse widths ofindividual transmission-side data do not meet the standard value range.That is, whereas the standard values for individual data are T=350μs-500 μs and 3T=1050 μs-1500 μs, such large-scale corrections ascorrecting T to 2T and correcting 3T to 5T as shown above would cause aproblem that the resulting transmission waveform deviates from the abovestandard value range.

[0007] As other countermeasures, there are some other methods in whichcorrection on the reception side is performed not by determining thepulse width with a threshold set at the generally center of thereception-side waveform, but by implementing reception-side correction,for example, by determining the pulse width at the rise and fall edgesof the waveform or by making the reception-side sampling intervalshorter, or other means. In these methods, however, the waveform itselfhas been deformed by the influence of noise or the like, posing aproblem of being inferior in performance to cases where the correctionis performed on the transmission side.

DISCLOSURE OF THE INVENTION

[0008] The present invention having been accomplished to solve the abovedefects of the prior art, an object of the present invention is toprovide a data transmission method capable of suppressing communicationerrors through simple microcomputer processing.

[0009] In order to achieve the above object, there is provided a datatransmission method in which specific data is made up of H and L levels,either one of which has a pulse width taken as a first fundamentalsignal length (T₁) and the other of which has a pulse width taken as asecond fundamental signal length (T₂) equal to an integer multiple ofthe first fundamental signal length (T₁), comprising the step ofperforming a correction of increasing or decreasing the secondfundamental signal length (T₂) by a length equal to an integer multipleof a value resulting from dividing the first fundamental signal length(T₁) of a transmissionside pulse signal by an integer.

[0010] In one embodiment of the present invention, the correction isapplied to pulse signals of an infrared remote control.

[0011] In this data transmission method, a correction is performed byincreasing or decreasing the second fundamental signal length by alength equal to an integer multiple of a value resulting from dividingthe first fundamental signal length of the transmission-side pulsesignal by an integer. This makes it possible to set correction amountsfor the lengths of pulse widths of individual signal levels in finesteps. As a result of this, it becomes possible to select correctionamounts that allow the standard values for the pulse widths of theindividual signal levels to be satisfied. Moreover, since the correctionamount for the second fundamental signal length is given by a lengthequal to an integer multiple of a value resulting from dividing thefirst fundamental signal length by an integer, microcomputer processingcan be simplified.

[0012] Also, there is provided a data transmission device in whichspecific data is made up of H and L levels, either one of which has apulse width taken as a first fundamental signal length (T₁) and theother of which has a pulse width taken as a second fundamental signallength (T₂) equal to an integer multiple of the first fundamental signallength (T₁), comprising:

[0013] division means for determining a value resulting from dividingthe first fundamental signal length (T₁) of a transmission-side pulsesignal by an integer; and

[0014] correction means for performing a correction of increasing ordecreasing the second fundamental signal length (T₂) by a length equalto an integer multiple of the value determined by the division means.

[0015] In this data transmission device, correction is carried out inthe following way. The division means determines a value resulting fromdividing the first fundamental signal length of a transmission-sidepulse signal by an integer, and the correction means increases ordecreases the second fundamental signal length by a length equal to aninteger multiple of the value determined by the division means. Thismakes it possible to set the correction amounts for the lengths of pulsewidths in individual signal levels in fine steps. As a result of this,it becomes possible to select correction amounts that allow the standardvalues for the pulse widths of the individual signal levels to besatisfied. Moreover, since the correction amount for the secondfundamental signal length is given by a length equal to an integermultiple of a value resulting from dividing the first fundamental signallength by an integer, the processing of a microcomputer equipped withthis data transmission device can be simplified.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] FIGS. 1A-1D are schematic diagrams showing the shapes of pulsesignal waveforms according to one embodiment of a data transmissionmethod of the present invention;

[0017]FIG. 2 is an arrangement diagram of the signal format forexplaining the data transmission method;

[0018] FIGS. 3A-3D are schematic diagrams showing the shapes of variouspulse signal waveforms;

[0019]FIG. 4 is a flow chart showing the flow of transmitting-signalprocessing according to an embodiment of the data transmission device ofthe present invention;

[0020]FIG. 5 is an explanatory view showing a data transmission methodaccording to the prior art; and

[0021] FIGS. 6A-6D are explanatory views showing a data transmissionmethod according to the prior art.

BEST MODE FOR CARRYING OUT THE INVENTION

[0022] A concrete embodiment of the data transmission method of theinvention will now be described in detail with reference to theaccompanying drawings.

[0023] FIGS. 1A-1D are schematic diagrams showing the shapes of pulsesignal waveforms according to one embodiment of a data transmissionmethod of the present invention. The constitution of signal format andthe standards of various types of signal pulses are generally similar tothose of the prior art shown above, and so their description is omitted.It is noted that the data transmission method in this embodiment isapplied to data transmission between a microcomputer incorporated in anelectric home appliance and an infrared remote control.

[0024] FIGS. 1A-1D show an example of the case where transmissionwaveform is corrected so that the reception-side waveform conforms tothe standards prescribed by the Association for Electric HomeAppliances. FIGS. 1A and 1B show the waveforms of “0” data and “1” data,respectively, derived from an infrared remote control, which is thetransmission side. FIGS. 1C and 1D show the waveforms of “0” data and“1” data, respectively, to be recognized by a microcomputer, which isthe reception side. This embodiment employs a correction method that theL level pulse width is increased by a length equal to an integermultiple of a value resulting from dividing the H level pulse width onthe transmission side by an integer (fundamental unit length t).Hereinbelow, the correction method for “0” data of transmission waveformis explained concretely. First, in the transmission waveform conformingto the standards for “0” data (see FIG. 3B), the H level pulse width istaken as a first fundamental signal length T₁ (not shown), and valueresulting from dividing this first fundamental signal length T₁ by 2 istaken as a fundamental unit length t. Then, a correction is performed byadding this fundamental unit length t to a second fundamental signallength T₂ (not shown), which is the L level pulse width, where theresult is taken as a new L level pulse width (see FIG. 1A). Since T₁ andT₂ in the “0” data basically have a relation that T₁=T₂, it is assumedthat T₁=T₂=T. From this relation, the ratio of H level pulse width to Llevel pulse width in the transmission waveform can be expressed as T:T+t(2t:3t) as shown in FIG. 1A. When this data is transmitted, a waveformin which the ratio of H level pulse width to L level pulse width on thereception side is generally 1:1 as shown in FIG. 1C is obtained.

[0025] Similarly, referring to “1” data, in a transmission waveformsatisfying the standards for “1” data (see FIG. 3B), the H level pulsewidth is taken as the first fundamental signal length T₁, and a lengthresulting from dividing this by 2 is taken as the fundamental unitlength t. Then, a correction is performed by adding a length 2t, doubleof this fundamental unit length t, to a second fundamental signal lengthT₂, which is the L level pulse width, where the result is taken as a newL level pulse width (see FIG. 1B). Since T₁ and T₂ in the “1” databasically have a relation that 3T₁=T₂, it is assumed that T₂=3T₁=3T.From this relation, the ratio of H level pulse width to L level pulsewidth in the transmission waveform can be expressed as T:3T+2t (2t:8t)as shown in FIG. 1B. When this data is transmitted, a waveform in whichthe ratio of H level pulse width to L level pulse width on the receptionside is generally 1:3 as shown in FIG. 1D is obtained.

[0026] Even in the correction of transmission waveform, considerationsare given so that the ratio of the sum of individual level pulse widthsin “0” data to the sum of individual level pulse widths in “1” data,i.e. (T+T+t):(T+3T+2t) in this case, meets the requirement for the ratioof 1:2.

[0027] Next, discussions are made as to whether or not each pulse widthof the corrected waveform on the transmission side satisfies thestandards prescribed by the Association for Electric Home Appliances. Inthis connection, since the transmission-side waveform is corrected sothat the pulse width of each level in the reception-side waveform hasthe fundamental signal lengths T₁ and T₂ falling within the ranges ofT=350 μs-500 μs and 3T=1050 μs-1500 μs, respectively, the receptionwaveform can be said to be compliant to the standard value ranges.Hereinbelow, it is examined whether or not the pulse widths of thecorrected individual data on the transmission side fall within thestandard value ranges 10%, that is, the ranges of T=315 μs-550 μs and3T=945 μs-1650 μs. In this embodiment, as shown in FIGS. 1A and 1B, theL level length of “0” data (second fundamental signal length T₂) iscorrected to T+t (=3t), and further the L level length of “1” data(second fundamental signal length T₂) is corrected to 3T+2t (=8t).Therefore, on the assumption that the fundamental unit length is t=180μs, substituting this for the above value yields 3t=540 μs and 8t=1440μs, showing that these pulse width values fall within the standard valueranges ±10%, respectively. Thus, it can be said that the correctedtransmission waveform substantially meets the standard value ranges.

[0028] As shown above, this embodiment of the data transmission methodincludes a correction that the second fundamental signal length T₂,which is the L level pulse width, is increased by a length equal to aninteger multiple of a value t resulting from dividing the firstfundamental signal length T₁, which is the H level pulse width, by aninteger on the transmission side. As a result, correction amounts forthe lengths of pulse widths can be set in finer steps than theconventional method where the pulse width of one level is set to aninteger multiple of that of the other level. Thus, it becomes possibleto select, from among the individual correction amounts derived by theabove-described method, such appropriate correction amounts that bothtransmission- and reception-side pulse widths meet the standard valueranges. In addition, since the degree of freedom for noise reducingmeasures on the reception side is enhanced by virtue of theimplementation that signals substantially conforming to the standardvalues can be transmitted and received as described above, it becomespossible to provide a capacitor having a large noise reducing effect orthe like. Further, since mis-recognition of signals becomes less likelyto occur, the communication error rate can be lowered. Furthermore,since the correction amount for the second fundamental signal length T₂is given by a length equal to an integer multiple of a value resultingfrom dividing the first fundamental signal length T₁ by an integer,microcomputer processing can be simplified.

[0029]FIG. 4 shows the flow of transmitting-signal processing accordingto an embodiment of the data transmission device of the presentinvention. This data transmission device transmits data by a pulsesignal having an H level width of a first fundamental signal length T₁and an L level width of a second fundamental signal length T₂ (e.g., T₁for “0” data, 3T₁ for “1” data) which is an integer multiple (e.g., 1for “0” data, 3 for “1” data) of the first fundamental signal length T₁.This data transmission device processes pulse signals of data code D₁,D₂, . . . D_(n) portions in FIG. 2 in a fashion shown in FIG. 4 andtransmits them, while signals of the other portions in FIG. 2, i.e.leader L, custom codes C₀, C₁, parity P and trailer TR, are the same asin FIG. 2. A microcomputer within the infrared remote control, which isnot shown, includes division means S1 for determining a value resultingfrom dividing the first fundamental signal length T₁ of a transmittingpulse signal by an integer, and correction means S2 for performing acorrection of increasing the second fundamental signal length T₂ by alength equal to an integer multiple of the value determined by thedivision means S1.

[0030] At step S1 in FIG. 4, the division means divides the firstfundamental signal length T₁, which is the H level width of the pulsesignal to be transmitted, by an integer (e.g., 2), calculating a value t(=T₁/2). Then at step S2 in FIG. 4, the correction means adds an integermultiple (e.g., 1 for “0” data, 2 for “1” data) of the calculated valuet to the second fundamental signal length T₂ (e.g., T₁ for “0” data, 3T₁for “1” data), which is the L level width of the pulse signal to betransmitted. Thus, for example, with the resulting ratio of the H levelpulse width to the L level pulse width being (T₁):(T₁+t) for “0” data or(T₁):(3T₁+2t) for “1” data, the pulse signal representing data istransmitted to the reception side (see FIG. 1A).

[0031] The pulse signal sent out from the data transmission device isreceived by the reception side as a pulse signal whose ratio of H levelpulse width to L level pulse width is generally 1:1 for “0” data orgenerally 1:3 for “1” data as described in conjunction with FIGS. 1A and3B for an embodiment of the data transmission method of the invention.Accordingly, each of the H and L level pulse widths conforms to thestandards prescribed by the Association for Electric Home Appliances onboth transmission and reception sides, exerting the same working effectsas in the already described data transmission method.

[0032] Although concrete embodiments of the data transmission method andthe data transmission device of the present invention have beendescribed hereinabove, the invention is not limited to theseembodiments. Instead, the invention can be carried out with variousalterations within the scope of the invention. For example, although theabove embodiments include a correction that the second fundamentalsignal length T₂, which is the L level pulse width, is increased by alength equal to an integer multiple of a value t resulting from dividingthe first fundamental signal length T₁, which is the H level pulse widthof the transmission waveform, by an integer, it is also possible toperform a reverse correction that the second fundamental signal lengthT₂ is decreased by a length equal to an integer multiple of thefundamental unit t. Further, although the above embodiments include thesetting that the first fundamental signal length T₁ is assigned to the Hlevel width and the second fundamental signal length T₂ to the L levelwidth, yet the above correction method may also be applied on thesetting that, reverse to the above embodiments, the first fundamentalsignal length T₁ is assigned to the L level width and the secondfundamental signal length T₂ to the H level for signals in which the Hlevel width is an integer multiple of the L level width. Further,although the above embodiments have been exemplified by a correctionthat the pulse width ratio for “0” data of transmission waveform iscorrected to T:T+t (2t:3t) and the pulse width ratio for “1” data iscorrected to T:3T+2t (2t:8t), yet the invention is not limited to thiscombination of ratios and various correction amounts may be selected sothat the prescribed standard values are met, for example, by dividingthe first fundamental signal length T₁ by 4 (T=4t) and setting the ratioto T:T+2t (4t:6t) for “0” data and T:3T+4t (4t:16t) for “1” data.Further, although the correction of transmission waveform has been doneso as to satisfy the standards prescribed by the Association forElectric Home Appliances in the above cases, yet correction amounts mayalso be determined so as to satisfy other standard prescriptions.Further, although the above embodiment has been described on atransmission method with an infrared remote control, the inventionmethod may also be applied to transmission methods with a wired remotecontrol or the like. Further, although the above embodiments have beendescribed on a method in which the transmitted waveform is inverted onthe reception side, that is, a method in which the waveform is receivedwith the H level taken as the L level and with the L level taken as theH level, the invention method is also applicable to methods involving noinversion of waveform, that is, methods in which the waveform isreceived with the H level taken as the H level and with the L leveltaken as the L level, in the same way as in the above case.

[0033] According to the data transmission method and the datatransmission device of the invention, since the correction amounts forthe lengths of pulse widths of signal levels can be set in fine steps,it becomes possible to select correction amounts that meet the standardvalues of pulse widths of individual signal levels. Furthermore, sincethe correction amount for the second fundamental signal length is set toa length equal to an integer multiple of a value resulting from dividingthe first fundamental signal length by an integer, the microcomputerprocessing can be simplified.

[0034] In addition, according to the present invention, since there isno need for using any plurality of timers, a low-priced microcomputerwill do for implementing the invention.

INDUSTRIAL APPLICABILITY

[0035] The data transmission method and the data transmission device ofthe present invention can be applied to not only electric homeappliances but also air conditioners.

1. A data transmission method in which specific data is made up of H andL levels, either one of which has a pulse width taken as a firstfundamental signal length (T₁) and the other of which has a pulse widthtaken as a second fundamental signal length (T₂) equal to an integermultiple of the first fundamental signal length (T₁), comprising thestep of performing a correction of increasing or decreasing the secondfundamental signal length (T₂) by a length equal to an integer multipleof a value resulting from dividing the first fundamental signal length(T₁) of a transmission-side pulse signal by an integer.
 2. The datatransmission method according to claim 1, wherein the correction isapplied to pulse signals of an infrared remote control.
 3. A datatransmission device in which specific data is made up of H and L levels,either one of which has a pulse width taken as a first fundamentalsignal length (T₁) and the other of which has a pulse width taken as asecond fundamental signal length (T₂) equal to an integer multiple ofthe first fundamental signal length (T₁), comprising: division means fordetermining a value resulting from dividing the first fundamental signallength (T₁) of a transmission-side pulse signal by an integer; andcorrection means for performing a correction of increasing or decreasingthe second fundamental signal length (T₂) by a length equal to aninteger multiple of the value determined by the division means.